{"id":51847,"date":"2025-09-09T18:28:20","date_gmt":"2025-09-09T09:28:20","guid":{"rendered":"https:\/\/phys-edu.net\/wp\/?p=51847"},"modified":"2025-10-13T05:22:50","modified_gmt":"2025-10-12T20:22:50","slug":"recrystallization-demystified-the-potassium-nitrate-and-sodium-chloride-lab","status":"publish","type":"post","link":"https:\/\/phys-edu.net\/wp\/?p=51847&lang=en","title":{"rendered":"Jewels Appearing Before Your Eyes! Uncover the Secret of Temperature Through the Recrystallization of Potassium Nitrate and Salt!"},"content":{"rendered":"

Ken Kuwako, Your Science Trainer: Every Day’s an Experiment!<\/strong><\/span><\/p>\n

Do you ever stop to think about “crystals” in your daily life? They’re actually all around us! Take the frost on your window on a cold winter morning, the intricate patterns of snowflakes, or even the tiny grains of sugar and salt on your table \u2013 all are small crystals. But how exactly do these wonders form? Most of us probably haven’t given it much thought.<\/span><\/p>\n

This time, we’re diving into an exciting experiment called “Recrystallization.” It’s a topic usually covered in junior high chemistry, and it’s all about creating crystals with your own hands \u2013 something we don’t often consciously observe in our daily lives. Specifically, we’ll learn how to extract crystals using potassium nitrate and sodium chloride. Through this experiment, you’ll get a firsthand feel for solubility and the effects of temperature, deepening your understanding of material properties. Let’s jump right into how it’s done!<\/span><\/p>\n

Experiment Steps<\/b><\/h3>\n

\u24ea Pre-Experiment Prep<\/b><\/p>\n

Prepare 3g of table salt (red) and 3g of potassium nitrate (blue) in separate weighing papers and place them in test tubes.<\/b> To speed things up, it’s a good idea to pre-measure the salt and potassium nitrate into weighing papers. I asked our science assistant to prepare these in advance, and it took about 30 minutes.<\/span><\/p>\n

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\u2460 Dissolving in Test Tubes<\/strong><\/p>\n

Place 3g<\/b> of each substance into separate test tubes. Then, add 5mL<\/b> of water to each. Submerge the test tubes in a beaker of hot water and gently shake to mix thoroughly. (I instructed students to put potassium nitrate in the blue-labeled tube and sodium chloride in the red-labeled tube.) Some students struggle to accurately measure 5mL with a pipette, so it’s important to provide prior guidance on how to hold and use a pipette correctly.<\/span><\/p>\n

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Potassium nitrate dissolves completely.<\/p>\n

Some groups of students, due to less efficient handling, had their hot water cool down, preventing everything from dissolving properly. We added more hot water for them, but this experiment takes a full 50 minutes, so timing is crucial. If not everything dissolves after a while, transfer approximately 2mL<\/b> of the supernatant liquid (the dissolved part) to a separate test tube (the one with the green label<\/b>).<\/span><\/p>\n

\u2461 Cooling the Solution and Observing<\/b><\/b><\/p>\n

Once everything in the blue-labeled tube (potassium nitrate) is dissolved, even if there’s undissolved material in the red one, place both test tubes into a beaker filled with water to cool them down. What happens next? The solute (solid component) in the potassium nitrate solution will start to appear as crystals! Once crystals form, place the test tube in a test tube rack and observe them. You’ll see beautiful, needle-like crystals.<\/p>\n

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Potassium nitrate crystals forming<\/p>\n

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No crystals appear from sodium chloride.<\/p>\n